Transformer thermal overloading is likely to occur during peak hours, emergency conditions, and/or during service restoration process. Transformer overloading over time accelerates insulation deterioration and may result in premature failures. The winding hot-spot temperature and the top-oil temperature are two important factors indicating the thermal condition of oil-immersed transformers. These two temperatures should be carefully monitored to mitigate the adverse effects of thermal overloading in the midst of rising load dynamics and variability in generation and demand.
Existing state-of-the-art methods determine the transformer steady-state rating based on conservative assumptions, disregarding the actual ambient temperature changes over time. This results in inaccurate estimation of the rating and under/over utilization of the transformer depending upon the actual ambient temperature. Existing practices for transformer overload monitoring rely on past and present current measurements and are not predictive in nature. Existing methods also do not account for the transformer oil and winding thermal inertia for dynamic rating estimation.